1. Field of the Invention
This invention relates to the field of foldable furniture, and in particular to foldable chairs having tubular frames and webbed support surfaces, commonly called lawn furniture or patio furniture.
2. Description of the Prior Art
The typical foldable patio chair as known in the art generally includes a back frame and a seat frame, both made of tubes bent in the shape of "U" members, pivotally attached to one another at a horizontal rod. When the chair is folded, the back and seat frames are pivoted toward one another; when the chair is opened, the back and seat frames are generally perpendicular to one another. The back frame and seat frame are carried on pairs of ground-engaging front legs and rear legs. The legs are often also made from tubes bent into a "U" and are pivotally attached to the back frame and seat frame at the frames and/or at armrests which are in turn pivotally attached to the frames. The leg members may be single legs, may be connected by cross-members, or may be formed in "U" shapes. The frames and legs are usually sheet metal tubing, for example, aluminum.
Patio chair constructions according to the foregoing general description are shown in U.S. Pat. Nos. 3,084-979-Moore; 3,316,013-Abel, et al.; and, 3,659,898-Yellin. In each of these examples, the rear leg member, that is, the "U" shaped leg member disposed under the back frame, is inclined forwards and used to support the chair when unfolded. A horizontal rod known as a spreader rod functions as a hinge pin in the pivotal attachment of the back frame and seat frame, and extends outwards beyond the back and seat frames, to rest on the rear leg member. When a user sits on the chair, the user's weight urges the spreader rod against the rear leg. The spreader rod and/or the seat and back frames are prevented from sliding down the tilting rear leg by means of a short linkage provided to pivotally connect the rear leg and rod or frames. This linkage is known as a "swing strap," and together with the other pivoting connections, makes the chair structure stable by virtue of the user's own weight.
The stability of folding lawn chairs is directly related to the urging of the spreader rod against the inclined rear leg. In folding and unfolding the chair, and in the various natural movements of users seated in the chair, the spreader rod is caused to slide over the contact point at the rear leg. The spreader rod, normally a solid metal bar, slowly but surely weakens the tubular aluminum rear leg member at the point of contact. Moreover, the leg members are normally constructed as "U" members, such that any axial movement of the spreader bar with respect to the rear leg (i.e., side to side movement) in fact flexes the entire chair, causing metal fatigue at the bends of the "U" members forming the legs.
According to the prior art such as the aforesaid patent to Moore, it is known to place a bushing over the extending portion of the spreader rod. Such a bushing increases the diameter of the spreader rod, spreading its force over a larger area of the rear leg. The bushing decreases damage to the leg due to abrasion because the bushing rolls rather than slides against the leg. Unfortunately, such a bushing fails to address the flexing caused by axial movement of the spreader bar over the rear leg, and the instability associated therewith.
U.S. Pat. No. 2,957,516-Kubisz discloses an appendage for the swing strap, that is, the linkage which pivotally connects the spreader bar and the rear leg. The appendage is a semi-circular sheet metal tab which engages the back of the rear leg when the chair is unfolded. Such a construction, although an improvement over devices which rest the spreader bar directly on the rear leg, relies upon the relatively weak sheet metal swing strap and its sheet metal appendage for basic structural support. The balance of the Kubisz chair is constructed of tubular sheet metal and solid bars. Therefore, the simple sheet metal swing strap, and the sheet metal appendage thereof, may be expected to suffer metal fatigue due to various flexings as the user naturally fidgets and moves about while seated in the chair. Kubisz's swing strap and appendage engaging the rear leg are likely to be the weakest links in the structural support.
U.S. Design U.S. Pat. No. Des. 268,314-Smith discloses a device which appears to be a swing strap in accordance with the Kubisz disclosure, but apparently places the opening for the spreader bar directly behind the semi-circular leg-engaging attachment. It is therefore unclear in Smith whether the semi-circular attachment or the protruding end of the spreader rod is in fact the load-bearing element. In the event that the semi-circular attachment is sufficiently rigid to bear the user's weight, the device is functionally identical to that of Kubisz. Therefore, Smith's swing strap would suffer from the same drawbacks in that structural support depends upon a relatively weak sheet metal member. Due to various axial and transverse movements of the spreader rod caused by a user's movements in the chair, the swing strap will suffer metal fatigue and eventually break. On the other hand, if Smith's semi-circular attachment is made resilient such that the spreader rod bears against the attachment, the spreader rod will slowly wear down the semi-circular attachment. Moreover, axial movement of the spreader rod and the resulting flexing will weaken the overall structure. In this event, the Smith device is functionally the same as the chairs of Moore, Yellin, and Abel, et al., in that the spreader bar will eventually damage the legs, and especially the contact point on the rear leg.
The present invention takes a different approach in that a leg-engaging contact pad in the form of a block is mounted directly on the extending end of the spreader rod. The contact pad, externally concave to complement the shape of the rear leg, not only cushions the spreader rod bearing against the rear leg, but also restricts the spreader rod from any axial movement with respect to the rear leg, that is, side to side with respect to the chair itself. Therefore, without relying upon any relatively weak single sheet metal structures, the device of the invention prevents damage to the rear leg by the spreader bar, and also restricts the chair from any side-to-side flexing which would eventually cause metal fatigue in the bends and joints of the legs.
The contact pad of the invention is constructed in a symmetrical fashion by which it fits equally well on either a left side or right side of the chair. Although the spreader rod fits axially through the contact pad, a transverse slot is provided such that a swing strap connecting the rear leg and the spreader rod can be suitably engaged and protected from flex. In an alternative embodiment, the contact pad further has a contoured end face which engages a further swing strap connecting the seat frame and back frame, thereby providing a resilient and protective connection at the most crucial junction of the folding chair.